- Circulating tumor cells (CTCs) are thought to break off from the original tumor and circulate in the blood.
- CTCs release proteins which could be used as biomarkers and these panel of proteins were measured using the microfluidic western blotting.
- The microfluidic device breaks the cells open and tests the cellular contents by introducing fluorescent probes that bind to and light up a specific protein target.
The study focused on individual tumor cells that float in the blood known as circulating tumor cells. The research team used microfluidic western blotting to measure a panel of cancer protein in these cells.
The new study was led by bioengineers at UC Berkeley.
‘Blood sample from cancer patients would allow doctors to monitor a patient's treatment response on a daily basis by identifying and testing proteins released from circulating tumor cells.’
Circulating tumor cells (CTCs) are rare tumor cells found in the circulatory system of certain cancer patients. The clinical and functional significance of CTCs are not fully known. Studying these cells is difficult because the cells are rare and only few are collected.
Circulating tumor cells are a potentially rich source of information about a person's cancer. These cells are thought to break off from the original tumor and circulate in the blood, and may be a sign of an aggressive tumor. The cells contain different proteins than the original tumor.
"Tremendous advances have been made in DNA and RNA profiling in cells collected using a liquid biopsy. We extend those advances to highly selective measurement of proteins - the 'molecular machines' of the cell," said Amy Herr, Berkeley a bioengineering professor and leader of the study team. "We are working to create medicine that would allow a doctor to monitor a patient's treatment response through a blood draw, perhaps on a daily basis."
Microfluidic Western Blotting
A key advance the team made was in devising a system to precisely handle and manipulate the concentrated cells from blood. They then analyzed each circulating tumor cell for the specific panel of cancer proteins.
The research team used microfluidic western blotting to measure a panel of proteins or protein biomarkers from isolated circulating tumor cells from patients with primary estrogen receptor-positive (ER+) breast cancer.
The microfluidic device separates these large cells into a concentrated sample. It breaks the cells open and tests the cellular contents for eight cancer protein biomarkers.
Each rare cell was placed in a microwell. Inside the microwell, the circulating tumor cells were burst open and the proteins released from inside each cell were separated according to differences in size or mass.
The scientists were then able to identify cancer proteins by introducing fluorescent probes that bind to and light up a specific protein target. By sorting and probing the protein targets, the test is more selective than existing pathology tools. Enhanced selectivity will be crucial in detecting subtle chemical modifications to biomarkers that can be important but difficult to measure.
"Microfluidic design was key in this study. We were able to integrate features needed for each measurement stage into one process," Herr said. "Systems integration allowed us to do every single measurement step very, very quickly while the biomarkers are still concentrated. If not performed exceptionally fast, the cell's proteins diffuse away and become undetectable."
The researcher team is planning to identify more proteins using this technology which will allow pathologists to classify cancer cells more precisely than is possible using existing biomarkers.
This test may one day help patients may be able to monitor their body's response to cancer therapy just by having their blood drawn.
The study is published in the journal Nature Communications
. The research was a collaboration with breast cancer surgeon Stefanie Jeffrey at Stanford University and with a University of California startup, Vortex Biosciences.
- Amy Herr et al. Profiling protein expression in circulating tumour cells using microfluidic western blotting. Nature Communications; (2017) doi:10.1038/ncomms14622